1. Field of the Invention
The invention relates to a shut-off valve for a tank.
The valve is suitable particularly for use in conjunction with a fuel tank for a motor vehicle, the shut-off valve being arranged in a filling path leading to the tank. However, it is also possible for the valve to be used for other tank installations, in order to avoid a tank overfilling.
2. Discussion of the Prior Art
In attempts to improve environmental protection, there is great interest in preventing the escape of gaseous phases located in a tank. On the other hand, it is often necessary to avoid a positive pressure being produced in the tank, it being possible for said positive pressure to be produced, for example, by the medium located in the tank being heated or by an external supply of heat. Air-extraction arrangements are provided in order to reduce the positive pressure. Such arrangements, for avoiding the escape of components which are damaging to the health, are equipped with appropriate filters. These air-extracting arrangements usually only allow slow, quasistatic pressure equalization.
Tanks which have their contents used up over time have to be refilled at various time intervals, for which purpose, in particular in the case of motor vehicle tanks, merely temporary connection to a filling line takes place. The tank has to be opened for refilling, in which case gases located in the tank may escape at the filling opening. In the prior art, for example in German reference DE 198 02 078 A1, the filling opening is provided with an automatically closing non-return valve which, when the filling line is removed, for example once a fuel-pump nozzle has been drawn out of a tank-filling opening, immediately closes the tank again. During filling, however, it is possible for gases located in the tank to penetrate outwards. This is countered in some cases by suction-extraction devices which are provided on sides of a filling arrangements and intercept the escaping gases.
During filling, it also has to be ensured that overfilling of the tank is avoided. The usual procedure is that in which, with a sudden rise in the delivery-opposing counterpressure, which takes place, for example, when the mouth opening of the fuel-pump nozzle is submerged in the filling-level surface of a tank or of a tank filler neck, the filling arrangement automatically switches off. In the above-mentioned DE 198 02 078 A1, the tank filler neck is designed to taper in the direction of the actual tank in order, when a maximum filling level is reached, to bring about a temporary build-up in the neck, this causing the filling arrangement to be switched off. The tapering design of the tank filler neck prolongs the time which is necessary for filling the tank. Moreover, the point in time at which the filling arrangement is switched off depends on a large number of influencing parameters, with the result that, in order to avoid overfilling, the tank filler neck is designed for an early switch-off operation. At this point in time, however, the tank is usually not completely filled, with the result that follow-up filling operations are necessary, these having to be carried out manually, in the case of conventional fuel-pump nozzles, and further prolonging the filling time.
In contrast, the object of the present invention is to provide a shut-off valve for a tank which, in addition to a high level of sealing in the closed state, allows quick, complete filling of the tank.
This object is achieved by a shut-off valve for a tank, comprising a filling tube with a filling-side valve seat and a tank-side valve seat. The seats are spaced apart from one another in the throughflow direction of the filling tube. The valve also has a valve body with a scaling element which can be moved between the valve seats in order, depending on the position of the valve body, to butt against either of the valve seats. The valve body is prestressed in the direction of the filling-side valve seat in order, in a rest position, to seal the filling tube in relation to the filling-side valve seat. It is possible for the prestressing of the valve body to be set such that it can be overcome by the flow pressure of a medium which is to be introduced, in the direction of the tank-side valve seat. A filling-level-controlled stop device is provided for stopping the movement of the valve body in the direction of the tank-side valve seat in a position in which the scaling element is kept at a distance from the valve seats such that the medium which is to be introduced can flow around the same. The stop action of the stop device is eliminated when a predetermined filling level in the tank is reached.
The solution according to the invention combines a high level of sealing with precise discontinuation of a filling operation when a predetermined filling level in the tank is reached, with the result that it is possible to dispense with laborious follow-up refueling operations. The closure of the valve body when the filling level is reached brings about a delivery-opposing, counterpressure which results in the filling arrangement being switched off. Since the closure of the valve body depends directly on the filling level in the tank, this precludes dynamic effects between the tank filler neck and the actual tank. In particular, in this case, it is no longer necessary for the tank filler neck to be designed with a cross section which tapers in the direction of the tank, with the result that the shut-off arrangement according to the invention, in addition, allows a wider tank filler neck and thus quicker filling.
By virtue of the prestressing of the valve body, in the rest position of the shut-off valve, sealing of the tank in relation to the surroundings is ensured on a permanent basis. On the other hand, filling can be carried out without any further measures being required on the valve, since the valve opens as soon as the flow pressure of the filling arrangement is applied. If the maximum filling level is not reached during a filling operation, then it is ensured that, following completion of the filling operation, the valve body immediately returns into the rest position in order to seal the tank in relation to the outside.
The sealing element may be formed integrally with the valve body or may be provided thereon as a separate element.
In an advantageous configuration of the invention, the valve seats are formed on inner-wall portions of the filling tube of which the inner width or diameter is greater than the inner width or internal diameter of a throughflow opening of the filling tube. This means that a large inner width of the filling tube remains for the filling operation. The flow resistance of the filling tube can thus be kept low, with the result that a filling operation can be carried out quickly, and without interruption, in particular also in the case of elevated temperatures.
The valve seats are preferably designed as wall portions which are inclined in relation to the throughflow direction. This makes it possible to achieve self-centering, of the sealing element in relation to the valve seats. Also achieved is good discharge of residual quantities of the filling a medium in the region of the valve seats in the direction of the tank.
In a further, advantageous configuration, the outer width or the external diameter of the sealing element is smaller than the inner width or the internal diameter of a widened tube portion arranged between the valve seats, but greater than the inner width or the internal diameter of the throughflow opening of the filling tube. By virtue of the widened tube portion, the flow resistance of the sealing tube in the region of the valve body is kept low, with the result that, even if relatively large quantities are delivered by the filling arrangement, premature switch off cannot take place. The cross sections of the tube portions in this case need not be round; they may also have other profile shapes.
In order to reduce the mass of the valve body, the valve body is designed as a hollow piston. This allows the valve body to be returned into the rest position even by way of low spring forces. This allows, in turn, filling to take place even at low delivery pressures. The flow resistance of the valve body can be further reduced if, according to a further, preferred configuration, on its end side which is oriented toward the filling-side valve seat, the valve body is designed as a convexity which tapers in the direction of the filling,-side valve seat.
In an embodiment that is particularly straightforward by means of design, and only has a small number of components, the valve body is guided with sliding action on an innerwall portion of the filling tube. The filling medium acts here as a lubricant, this giving particularly smooth-running mounting of the valve body, with the result that the returing forces for sealing the tank can be kept low and/or the valve body can easily be moved by the flow pressure into a switch-off position, in which the sealing element comes into abutment against the tank-side valve seat.
The valve body is preferably supported against the inner wall of the filling tube via a spring, of which the prestressing is set such that the valve body is automatically pressed with sealing action, by way of its sealing element, against the filling-side valve seat. The sealing can be eliminated by the flow pressure of a medium which is to be introduced.
In a further, advantageous configuration of the invention, the region between the valve seats is connected to a portion of the filling tube and/or of the tank downstream of the tankside valve seat via an overflow line which takes effect when the sealing element butts against the tank-side valve seat and has a defined throttle location for slow pressure equalization. It is thus possible, following closure of the valve body against the tank-side valve seat, for medium located in the filling tube downstream of the tank-side valve seat to be discharged slowly into the tank until the valve body is returned into abutment against the filling-side valve seat again.
A spatially compact and also robust design which is not susceptible to malfunctioning is obtained by the stop device being configured with a displaceable stop protrusion which is intended for stopping the movement of the valve body, which is arranged in a tube portion of the filling tube between the tank-side valve seat and the tank, against which a supporting element of the valve body butts in a stopped position, and which is coupled to a filling-level signaling device. In dependence on the filling-level signaling device, when a predetermined filling level in the tank is reached, the stop protrusion is moved out of its stop position in order to release a further displacement path for the supporting element of the valve body. An example of a possible filling-level signaling device is a float which is arranged in the tank and, when a certain filling level is reached, produces a mechanical or electrical signal which is converted into an actuating signal for the stop protrusion. This can take place, for example, via a mechanical linkage which connects the float to the stop device. Instead of the mechanical linkage, it is also possible to use an electrical actuating element for actuating the stop device.
The stop device preferably comprises a flap which can be pivoted about a pin in the direction transverse to the throughflow direction and which has an opening which upon displacement of the stop protrusion, as a result of a predetermined filling level in the tank being reached, can be pivoted into the position of the stop protrusion. The switch-off operation can then be brought about, in a manner which is particularly straightforward in terms of design, when the filling level is reached. During the filling operation, the supporting clement of the valve body remains supported on the stop protrusion until such time as the stop protrusion is pivoted out of its supporting position. It is replaced by the opening, through which the supporting element of the valve body penetrates, with the result that the supporting element is moved in the direction of the tank again, whereby the sealing element of the valve body passes into abutment against the tank-side valve seat and causes the filling arrangement to be switched off.
In order to simplify the production, the flap of the stop device is designed as a plate-like element, for example as a sheet-metal element, with a border portion which is bent about the transverse pin as the stop protrusion, against a supporting surface of which the supporting element of the valve body can be brought into lateral abutment. The opening on the plate-like elements adjoins the stop protrusion in order to pass into the position of the supporting surface when the plate-like element is pivoted about the transverse pin, the opening being larger than the supporting surface. The plate-like element may be produced, for example, as a straightforward bent sheet-metal part.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.